350 JOURNAL OF COSMETIC SCIENCE untreated sebum Figure 14. Images ooe untreated hair and hair treated with synthetic sebum. Amount ooe treatment was ! g ooe 5% solution per 3-gram tress. Exposure values: oe8 and !/6 s. 25O 2OO • 15o 'i .• 100 50 w i i i 0 10 2o 3o 4o 5o Distance (ram) Figure 15. Light distribution curves for untreated hair and hair treated with synthetic sebum.

LUSTER QUANTIFICATION OF HAIR 351 exposure modes, were converted into light distribution curves similar to those obtained in goniophotometer experiments (1,3,4). Several equations, empirically verified by vari- ous authors, were utilized to calculate the luster parameters. The results were generally consistent with the literature data and visual observations. It was shown that: © Natural white, light blonde, light brown, medium brown, and dark brown hair showed a gradual increase in luster proportional to the amount of melanin pigmen- tation. Light-colored hair clearly displayed two specular reflection bands correspond- ing to the front- and back-face reflections from hair fibers. © Silicone and hydrocarbon oils, specifically phenyl trimethicone, amodimethicone, and castor oil, increase the luster of hair by enhancing the contrast between specular and diffuse areas. Phenyl trimethicone was found to be the most effective treatment. © Luster can be increased by the deposition of polymers, such as hairspray or styling resins, forming thin films on the hair surface. © A controlled reduction in hair luster can be achieved by deposition of various amounts of micronized ZnO, which increases the width and intensity of both specular and diffuse reflection from hair. Additionally, a decrease in luster was demonstrated with the use of a synthetic sebum. ACKNOWLEDGMENTS The authors acknowledge help in performing experiments from S. Chen and many useful discussions with C. Rocafort and L. Foltis. This paper is dedicated to the memory of Dr. Robert Stamm who performed pioneering studies in this area. REFERENCES (1) R.F. Stamm, M. L. Garcia, and J.J. Fuchs, The optical properties of human hair. I. Fundamental considerations and goniophotometric curves, J. Soc. Cosmet. Chem., 28, 571-599 (1977). (2) R. F. Stamm, M. L. Garcia, and J. J. Fuchs, The optical properties of human hair. I. The luster of hair fibers, J. Soc. Cosmet. Chem., 28, 601-609 (1977). (3) W. Czepluch, G. Hohm, and K. Tolkiehn, Gloss of hair surfaces: Problems of visual evaluation and possibilities for goniophotometric measurements of treated strands,J. Soc. Cosmet. Chem., 44, 299-318 (1993). (4) C. Reich and C. R. Robbins, Light scattering and shine measurements of human hair: A sensitive probe of the hair surface, J. Soc. Cosmet. Chem., 44, 221 (1993). (5) H. K. Bustard and R. W. Smith, Studies of factors affecting light scattering by individual human hair fibers, Int. J. Cosmet. Sci., 12, 121-133 (1990). (6) T. Maeda, T. Hara, M. Okada, and H. Watanabe, Measurements of hair luster by color image analysis, 16 t•5 UFSCC Congress, New York, 1990, Vol. I, p. 127. (7) C. Scanavez, M. Zoega, A. Barbosa, and I. Joekes, Measurement of hair luster by diffuse reflectance spectrophotometry, J. Cosmet. Sci., 51, 289-302 (2000).